Telephone system



Oct. 18, 1938. G. T. BAKER ET AL TELEPHONE SYSTEM Filed June 22, 1936 s sheets-sheet 1 W .l W wel, N. A@ v .Y vd ....w WV MM Oil. .Ol |111 H1 ov DIA v w ...H ....M.... ...n.r... u H u A ...N S .m MM m m W m u R .Hl Il m H lll l c .Il M C u n 0| .i rw z M1 u Nw DMn In ab 7.16 1 p 6W AT M 4u Y i 0h 3v. m a v R l y .1.. u u F E LW/ f 1% P IIl #AT1 H l. C L/S W m m E F.: s c ..12 wv u M., Pw m H W. |L v P UM l am lll lcs G. T. BAKER ET AL TELEPHONE SYSTEM Oct. 18, 1938.

Filed June 22, 1936 3 Sheets-Sheet 2 Oct, 18, 1938. G. T. BAKER ET AL TELEPHONE SYSTEM 5 sheet-sheet 5 Filed June 22, 1956 Vo CoNTRoL SET ICS Patented oei. 18, 193s 2,133,415

UNITED STATES PATENT OFFICE 42,133,415 TELEPHONE sYs'rl-:M

George Thomas Baker and John William McClew, Liverpool, England, assignors to Associated Telephone & Telegraph Company, Chicago, Ill., a corporation of Delaware Application June 22, 1936, Serial No. 86,574 In Great Britain August 9, 1935 15 Claims. (Cl. 179-18) The present invention relates to telephone show a. subscribers line circuit in association systems and is more particularlyV concerned with with a line finder connected to a. common conline finder systems employingy an arrangement. trol set CS by way of a single motion allottery suitable for use in a small exchange `wherebyI AS, whilev Fig. 3 shows the line circuit associated 5 junction lines as well as subscribers lines apwith a junction. The. line iinder switch is as- 5 pear in the banks of the nnder switches. If the sumed to be of the, two-directional type which nclers are of the large capacity type, difficulties performs a so-called rectangular movement in may arise in known arrangements in obtaining operation and uses one of the setting magnets to suiliciently speedy operation in the case of juncrestore it to normal. Levels l and 2 of the line,

1o-tion connections where only the inter-digital finder shown accommodate the junction line cr- 10 pause is available and there is no question oi cuits each of which appears. in b0th1eV61S.1eVe1S waiting for dial tone as when a subscriber is. 3 to 6 accommodate ordinary subscribers line calling. The chief object of the inventionL is circuits while levels I and 8 may accommodate to provide an improved arrangement for enabling either COH bOX 01' Ordinary Subscribers, discrlmi v impulses to be successfully received over a. juncnation being made by a strapping change in the 15' tion before the finder has completed its operaline circuit concerned. Level 9 is used for routine tion. It will be understood that the term juncpurposes and no line circuits are accommodated tion refers to a trunk line from a distant exon this level. Two control sets and two allotters change. are provided per group of lines accessible to a. 201. According to one feature of the invention in a iinder switch, the arrangements being such that telephone system employing finder switches for each control set serves hali the group in normal connecting calling lines to numerical switches, circumstances. during the operation of a finder the calling line Referring t0 Figs 1 Mld 2, a circuit descripis connected to the associated numerical switch tion of a call originated by an ordinary subindependently of the wipers of the nder, the scriber will rst be given, the particular line marking in the finder bank corresponding to the terminating in level 3 0f the ndel bank- When calling line being characteristic of the nder the receiver is removed the loop extended over employed so that in the event oi simultaneous the incoming negative and pOSitiVe ConduCtOrS calls the finders used will connect with the proper operates relay L which thereupon at armature ll 3o lines. i extends a level marking battery by way of re- 30 According to another feature of the invention sistance YA to the finder vertical benk multiple in a telephone system employing iinder switches and at the same time operates the start relay to the banks of Which'are connected both sub- ST in the control set CS. by Way 0f the upper scribers lines and junctions from another exhalf of rectifier MRA. Armature l2 marks the change, during the operation of a finder due to position of the calling line in the nder P bank 35 a call incoming over a junction the junction is multiple and armature Z3 disconnects the windconnected to a numerical switch independently ing 0f relay K frOm the P lead 0f the final Seof the wipers of the nder to enable dialled imlector multiple in order to busy the line to inpulses to be received over the junction. coming calls.

' 4o A further feature of the invention is that in Relay ST upon operating, at armature stl come 4o a telephone system employing two-directional pletes a circuit for relay LK from earth over its finder switches to the banks of which are conright-hand low resistance winding, Wiper 3, finder nected'both subscribers lines and junctions from olf-normal springs NI, link T, P lead to idle another exchange, the junctions are each conmarking battery in the associated selector (not nected to a plurality of levels of the nders, the shown). Relay LK Operates in this Circuit and 45 number of such levels corresponding to the numthe low resistance of its right-hand winding ber of iinders, having access to a particular group provides an immediate guard on the outlet seized. of lines, which are adapted to hunt simultane- It should be mentioned that in the absence 0f ously. calls free finders are preselected by the allotter The invention will be better understood from as will be described later. Armature llcl there 50 the following description of one method of carryupon disconnects a possible operating circuit for ing it into effect, reference being had to the acthe allotter magnet AM and completes a lockcompanying drawings comprising Figs. 1, 2 and 3 ing circuit for relay LK in series with relay VR which should be arranged with Fig. 2 to the and magnet AM which is non-operative in this right of and Fig. 3 below Fig. l. Figs. 1 and 2 condition, Relay VR operates and energizes re- 55 tical magnet VM Which causes the inder to hunt` vertically for the marked level. The off-normal springs VN I and N2 operate on the first vertical step and at springs NI extend a further guard earth to wiper 3.

As soon as the markedA level is encountered,

the fast operating relay VT in the control set is,`

energized over wiper 5, vertical wiper VW and bank VB to the level marking battery'by Way of resistance YA.

diately guards the level against seizure by another finder. Armature 'Utl disconnects kthe vertical magnet driving circuitreleases relay H and completes an operating circuit for relay RS. As a result of the release of relay H a self-interrupted driving circuit is completed for the rotary magnet RM from earth on common lead I by way of delayed release alarm equipment, rotary magnet interrupter springs rm, off-normal springs N2, armature h6 and rotary magnet RM to battery and accordingly the wipers are rotated in search of the calling line. At the com= mencement of rotary motion the rotary oilnormal springs NRI and NR2 operate.

When the calling line is encountered a circuit is completed to jam the rotary magnet from earth, armature rsI, wiper 6, upper low resistance winding of relay H, P wiper, armature Z2, vertical bank VB and wiper VW, interrupter springs rm, off-normal springs N2 and armature h6 to hold operated the rotary magnet RM and thus prevent further rotation. Relay H operates in this circuit and at armatures hl, h2, h3 and h4 extends the negative, positive, M and P leads through to the selector while armature h6 opens the magnet jamming circuit and completes a,

holding circuit for relay H by way of its lower winding, springs NR2 and armature h4. Earth by way of springs NRI and armature h is now extendedover wiper 4 to energize magnet AM and to short-circuit relays LK 'and VR in order to free the control setv for further use.

In response to the -extension of the calling loop through to the selector, the line relay therein is operated and operates the release relay which returns'a guard earth over the P conductor to hold relay H afterV the control set is released. Earthis also returnedrover the M conductor to operate relay K which thereuponl operates and at armature k3 locks in series with'the upper winding of relay H to the earthed P lead and at armature klV operates relay P which extends the M lead through to the subscribers meter MTR which operates when subsequently ,the called subscriber answers. Armatures kl and k2V at the same time open the circuit of relay L which releases and removes the level marking battery at armature Z I in order to release relay ST in the control set.l Dial tone is now returned to the calling subscriber over the line conductors to inform him that the circuit is ready to respond to the dialled impulses. Relays LK and VR in the control set nowY release due to the shortcircuiting effect of armature h5 .and in turn release relay RS. Armature T33l opens the circuit of the magnet AM which de-energizes and steps Y In this case the low resistanceA earth through the winding of relay VTimmethe allotter Wipers on to the next contact in readiness for a further call.

Under normal light traffic conditions it may be assumed that no further call will be originated for a short period and in the meantime the control set is arranged to preselect a free nder and associated selector under control of relay G. Should the finder on to which the allotter has been stepped be engaged, an earth from the operated oil-normal springs NI in this nder will be extended over wiper 3 to operate relay G in series with relay LK which however will not operate in this instance. Armature gl energizes the magnet AM which opens its interrupter springs am and opens the circuit of relay G. This relay thereupon releases and disconnects the magnet which again advances the wipers one vstep and closes its interrupter springs.

Should the allotter wipers again encounter an engaged iinder, the same operation will occur and interaction .between relay G and the magnet will continue until a free finder is reached. If, however, a further call originates before the completion of preselection, relay ST will be operated and armatures stl and st2 change over the relay magnet drive to a self-interrupted drive in order to reduce the allotter hunting time. As soon as the allotter encounters a free finder, relay LK will. operate to the idle marking battery in the associated selector and disconnect the drive and the circuit operation then proceeds as already described.

In the case of faults known as P. G.s which result in the simulation of a calling condition, it is arranged that the selector institutes forced release conditions a predetermined time after seizure if no impulses have been received. lThese conditions result in the removal of earth from Ythe P conductor which restores relay H in the finder and relay K in the line circuit. Relay P, which is made slow releasing by a short-circuited winding, will remain operated during the release transit time of relay K and subsequently its operating circuit will be maintained from the fault over the subscribers loop and armatures k2 and pI. This condition obtains until the fault is cleared and the line is thus isolated from the exchange equipment. If desired an alarm may be given by the continued operation of relay P with relay K de-energized. The finder is restored to normal on the release of relay H as described later.

In order to eiect economy in selectors it is arranged that they are shared by both subscribers and incoming junctions, the latter being connected to the iinder bank levels I and 2 by way of a relay set such as that shown in Fig. 3. This includes line and cut-off relays IL and IK and also two additional testing relays HA and HB, the vfunction of which is to route the call to a particular one of the two control sets. Y To even up the load it is arranged by a simple strapping connection between the switching relays HA and HB and conductors TA and 'I'B that odd numbered junctions have preference for the rst control set and even numbered junctions have pref-V erence for the second, but in either case connection is made with the other control set if the preferred one is already engaged.

When a call arrives over the junction, the loop extended to the incoming negative and positive conductors operates relay IL which .at armatures IZ I and IZ2 prepares operating circuits for relays HA and HB. Assuming now that the iirst control set CS which is rst choice for this junction is free, earth is extended from armature w3 therein, conductor TA, armature IZI, windings of relay HA in series, armatures IM and hb5, conductor T, to battery through resistance YE in the control set CS. Relay HA operates and at armature ha3 short-circuits its upper high resistance Winding thereby extending a low resistance guarding and holding potential on to conductor T to prevent another relay corresponding to relay HA from switching thereto. Relay HA also at armature haB extends a resistance marking battery on to the start lead ST, at armature ha5 disconnects the circuit of relay HB, at armature had supplies a marking to the finder P bank over conductor RMI and at armatures hal and ha2 switches the incoming negative and positive leads through to the control set.

If however the first control set was in use, relay VR would be operated and there would be no earth on conductor TA for operating relay HA. In case the seco-nd control set ICS was free the operation of relay VR in thefirst control set CS would result in the connection of earth over armature 'url to conductor TB associated with the second set and therefore a circuit would be completed to enable relay HB to operate over this conductor and function in a like manner `to relay HA except that' the incoming leads are switched through to the second control set ICS and marking is applied to conductor RMZ instead of RMI.

As a result of the operation of relay HA, the resistance battery applied tothe conductor ST causes relay ST in the control set CS to operate and relays LK and VR therefore immediately energize to switch the control set through to a preselected finder. The finder therefore commences its hunting operation as for an ordinary subscribers call but in these circumstances armatures vr6 and Url extend the incoming junction negative and positive leads direct over the allotter wipers I and 2 to the selector associated with the finder taken into use and therefore it is able to respond to any incoming impulses at once. 'I'he finder now commences to hunt vertically and it will be noticed that armature W2 extends the level marking battery over wiper 1 to vertical bank contact I while the rotary jamming circuit is completed over conductor RMI and'armature had in Fig. 3. In case the second control set had been taken into use, relay HB would have operated and similar operations would have been performed except that armature IvrZ marks vertical bank contact 2 and armature hb4 (Fig. 3) completes the rotary jamming circuit by way of level 2 and conductor RM2. Corresponding contacts of levels I and 2 are multipled together so that each junction makes an appearance in both these levels.

In the case of simultaneous calls one junction relay set will switch by way of conductor TA to control set CS and the other relay set Will switch by Way of conductor TB to control set ICS or viceversa thus causing the finders taken into use to hunt over different levels. It will be appreciated that the drive stopping circuits are divided at the vertical bank so that there is no possibility of a finder becoming associated with a different junction line from that which is linked to the associated selector through the allotter over wipers I and 2.

When the finder has found the calling junction and switched through, the negative, positive, M and P leads are connected straight through to the selector and the temporary by-path dialling circuit through the allotter is disconnected with the release of that equipment. Upon the operation of relay IK in Fig. 3 the switching relay which was previously operated is released.

The junction relay set, Fig. 3, may readily be arranged to return busy tone to the subscriber in case further dialling occurs before a selector can be connected to the junction; this condition would arise if both the control sets were already in use at the moment a call arrived over the junction.

Referring again to Figs. land 2, it is arranged that a maximum of ten line circuits may serve either coin box or ordinary subscribers; these line circuits appear in both levels 'I and 8 corresponding contacts of which are multipled together. Contacts 2lI and 212 shown in Fig. 1 are assumed to be carried by a line relay 2L of a line circuit in this group. If for example iive of these line circuits serve ordinary subscribers, the level and rotary markings will be extended by way of suitable jumpering to level lfwhile the remaining five which serve coin box subscribersv will be marked on level 8. On calls originated by the five ordinary subscribers therefore the Ender will hunt over level 'I until it encounters the rotary marking extended by way of the regular strapping and on calls originated by coin box subscribers the finder will hunt over level 8. Due to the separation of the stopping circuits as in the case of the junction lines, there is no possibility of hunting over an incorrect level, this being important since it is desirable to give a discriminating signal when a coin box subscriber originates a call. Normal post springs NPI are arranged to operate on the 8th level and a discriminating battery by Way of resistance YF is therefore connected to the CB conductor extending to the selector to inform the operator of the class of the subscriber originating the call where it is routed to the manual board.

At the conclusion of conversation, when the calling subscriber replaces his receiver, earth is removed from the P conductor. Relay K in the line circuit releasesand lreleases relay P while relay H in the finder is also released. At armature h6 a self-interrupted driving circuit for the rotary magnet is again completed and the switch thereupon rotates to the 12th position in which the wipers are clear of the bank. In this position the supporting means for the wiper carriage are no longer operative and it falls by gravity assisted by a spring and then rotates back to the normal position whereupon the off-normal springs N2 open and disconnect the rotary magnet. The guarding earth extended by springs NI to the allotter bank is then removed and the finder becomes available for further use. Preferably while the switch wipers are falling and rotating back to normal the rotary magnet interrupter springs are prevented from opening so that the magnet remains energized and does not chatter.

Should the calling subscriber restore his receiver during the inding operation, the marking battery on the vertical and rotary bank multiple will be removed and relay ST in the control set will be released thus releasing relays LK and VR at armature st3 if `the finder has not completed its vertical movement. In this case armature 121-4 Will disconnect the vertical magnet circuit and open the circuit of Vrelay H. Armature h6 thereupon completes 'a self-interrupted circuit for the rotary magnet and the finderV will cut in on the particular level at which it stopped and the subscriber hangs up, relays LK, VR and RS remain operated until the switch rotates to the 11th position where a magnet jamming circuit is completed and relay H in the finder operates over its upper low resistance winding. Armature h6 disconnects the magnet jamming circuit and armature h extends earth over wiper 4 to energize the magnet AM and short-circuit and release relays LK and VR. Relay VR upon releasing releases relay RS which opens the circuit of the allotter magnet AM which then steps the wipers I to "l, of the switch AS, to the next contact in readiness for a further call.

Armature rsl opens the holding circuit of relay H which then releases and causes the nder rota-ry magnet to step the switch to the 12th position whereupon it restores to normal.

Should the finder fail to iind a vertical marking, it will step to the ninth level and relay VT will be operated by the marking battery permanently connected toV this level by Vway of spools YG and YH. The wipers will then cut in, rotate to the 12th position and release. Since the start signal is maintained, as soon as another finder is selected by the allotter the hunting operation will be repeated.

In case all iinders become busy, all the idle imarking batteries normally extended over the various selector P leads by way of off-normal springs Nl and N3 and high resistance YC to the common lead extending to relay OFB will be disconnected at the finder olf-normal springs. Relay OFB will therefore release and operate its relief relay OFR which opens the driving circuits of both allotters at armatures ofrl and ofr3 to prevent useless hunting, while armatures ofr2 and ofr4 prepare circuits for the overflow meters associated with the control sets so that Yfurther calls originated during this period are recorded.

In case a control set is removed during maintenance, shelf jack points UH and Ul2 in the control set concerned are arranged to make contact so that the start relay ST in the remaining control set can serve all the subscribers in the group. 1

Rectiers MRA to MRC are inserted in the start leads to prevent marking battery from feeding back to other vertical bank contacts and thus causing a finder toV stop at an incorrect level.

We claimz- 1. In a telephone system, calling lines, nder switches having bank contacts terminating said lines, wipers on said iinder switches for connecting with said lines by way of said contacts, a numerical switch associated with each of said inder switches, means responsive to calls on said lines for marking the iinder bank contacts corresponding to the lines calling and for'taking said iinder switches into use one Vfor each call, each of said markings being individual to the particular finder switch taken into use by one call to enable said iinder switches in case of simultaneous calls to iind and connect with the proper lines, and

means for connecting the calling lines 'independently of the nder switch wipers to the numerical switches associated with the particular finder switches taken into use-during the operation of such inder switches in search of the calling line. 2. In a telephone system, iinder switches hav-V ing wipers and bank contacts accessible thereto, lines of a iirst class and lines of a second class terminating in said bank contacts, means responsive to a call on any one of said lines for operating the wipers of one of said finders to find and connect with the calling line by way of said bank contacts, a numerical switch associated with each of said iinder switches, and means operative only in case said call is of the second class for connecting the line independently of the nder switch wipers to the associated numerical switch to enable dialled impulses to be received over said line prior' to the connection of said finder switch with said line.

Y 3. In a telephone system, two-directional finder switches having Wipers and levels of bank contacts accessible thereto, subscribers lines and trunk lines terminating in said bank contacts, each trunk line being multiplied to the bank contacts in a plurality of trunk line levels, and the number of multiplied trunk line levels corresponding to the number of nder switches which may be simultaneously operated to nd the lines calling.

4. In a telephone system as claimed in claim 1 including an allotter for taking an idle one of said finders into use and for applying said marking individual to the finder taken into use.

5. In a telephone system as claimed in claim 2 including an allotter for taking an idle one of said finders into use, andwipers on said allotter for connecting said trunk line to said numerical switch independent of the finder wipers.

6. In a telephone system as claimed in claim 2 including a plurality of allotters each having access to all the nder switches for allotting idle ones of saidrnder switches for use, each allotter.

being first choice to certain of said trunk lines, and all allotters being simultaneously operable to take into use a plurality of said iinder switches.

7. In a telephone system, two-directional iinder switches each having levels of bank contacts ac-Y cessible thereto, trunk lines terminating in said bank contacts, a plurality of allotters for allotting idle'ones of said nders for use, each allotter being iirst choice to certain of said trunk lines and normally allotting a iinder for use thereby, each trunk line being multipled in a plurality of levels in the bank contacts of each iinder, means responsive to a call on any one of said lines for operating the allotted iinder switch in Vsearch of the calling line, and means also responsive to said call for marking the calling line in a certain one of said levels in case the corresponding first choice allotter is available or for marking the calling line in another one of said levels in case said iirst choice allotter is unavailable.

8. In a telephone system, two-directional nder switches having levels of bank contacts, subscribers lines and trunk lines terminating in different levels in said bank contacts, a vertical bank contact for each level of bank contacts in each finder switch, an allotter forallotting an idle one of said nder switches for use, means responsive to a call on any one olf said subscribers lines or said trunk lines for operating the allotted finder in search of the calling line, individual subscriber controlled means responsive to a call on one of said subscribers lines for directly marking the vertical bank contact corresponding to the level terminating said calling subscribers line, and means including a wiper on said allotter for marking the vertical bank contact corresponding to the level terminating the calling trunk line in response to a call on one of said trunk lines.

9. In a telephone system as claimed in claim 8 including a start lead individual to each level for applying said marking potential to said vertical wherein certain of said subscribers lines are di' vided into two different classes, said certain lines being multipled in a plurality of levels of bank contacts, means for causing the finder to search over one of said levels for lines of one class and over another of said levels for lines of a different class whereby the lines of one of said classes may be readily changed to lines of the other class.

12. In a telephone system, calling lines, finder switches having bank contacts terminating said lines, wipers on said finder switches for connecting with said lines by Way of said contacts, a numerical switch associated with each of said iinder switches, means responsive to the initiation of a call on one of said lines for taking any one of said nder switches into use and for marking only the bank contacts of said one nder switch, said marking corresponding to the calling line.

13. A telephone system as in claim 12 including means for connecting the calling line to the numerical switch associated with said one finder switch independently of the iinder switch wipers.

14. In a telephone system, calling lines, a groupof finder switches having bank contacts terminating said lines, wipers on said nder switches for connecting With said lines by Way of said contacts, a numerical switch associated with each of said finder switches, means responsive to the initiation of a plurality of simultaneous calls on said lines for simultaneously taking into use a finder switch for each of said calls, means for connecting each calling line to one of said numerical switches independently of the finder switch wipers and means for causing the wipers of each finder switch to engage only the bank contacts terminating the line to which the numerical switch associated with said nder switch is connected.

15. In a telephone system, calling lines, a group of finder-selector links having finder bank contacts terminating said lines, finder switch wipers for connecting with said lines by way of said contacts, means responsive tothe initiation of a plurality of simultaneous calls on said lines for si multaneously taking into use one of said links for each of said calls, means for connecting each calling line to one of said links independently of said nder switch wipers, and means for setting the finder switch wipers of each link on only the nder bank contacts terminating the line to which the link is connected.

GEORGE THOMAS BAKER. JOHN WILLIAM MCCLEW. 

